1. Field of the Invention
THIS INVENTION relates to improvements in drilling equipment.
2. Description of the Prior Art
The operator of a drilling rig must operate the rig under a number of conflicting conditions. As he is paid by the meter depth drilled, a high drilling rate increases his operating profit on the rig. However, a loss of the drilling equipment (e.g. the hammer and/or drilling bit) down the hole can result in a monetary loss of $50,000 (Aust.) plus, easily cancelling the operating profits.
Generally the drilling equipment is lost due to a collapse of the hole wall above the drilling equipment, the dislodged material jamming the drilling equipment down the hole. The collapse may be due to a physical failure in the soil stratum around the hole, or the dislodgement of rocks or soil from the wall of the hole by the drilling equipment as it is withdrawn from the hole or while geological samples are being taken. In certain areas of Western Australia, the clay strata at a depth around the hole swells to "choke" the hole, when contacted by ground water from another level in the hole.
When the hole wall collapses, or the clay chokes the hole, the operator either has to abandon the drilling equipment down the hole or use a second rig to try to recover the equipment by drilling a second hole closely adjacent the first. It will be readily apparent to the skilled addressee that the second rig could suffer the same fate as the first rig.